1. Field of Art
The invention relates to a method for the operation of a combustion device, in which liquid hydrocarbons are mixed with primary air and the mixture is conducted into a reaction chamber where it is contacted with shaped metal bodies and subjected to elevated temperature to convert the mixture into a soot-free fuel gas mixture containing carbon monoxide, hydrogen and gaseous hydrocarbons which is mixed with secondary air and fed into the combustion device.
2. Prior Art
In the combustion of liquid fuels in combustion devices such as burners or internal-combustion engines, uneven mixing and combustion of the fuel with the air leads to high emission of harmful substances in the exhaust gas. If these fuels contain lead, or aromatics, these substances which are injurious to health are also contained in the exhaust gas. It is known that the emission of harmful substances can be lowered if the combustion device is preceded by a gas generator in which the fuels are reacted with primary air under heavy air deficiency forming a fuel gas. Such a procedure is described, in detail in U.S. Pat. No. 3,828,736 in which liquid hydrocarbons are gasified, and the resulting gasified hydrocarbons are mixed with air. The resultant hydrocarbon/air mixture is conducted over nickel sponge or platinum catalyst arranged in the reaction chamber.
Unleaded straight-run gasoline with a low octane number can be used and can also be converted into a fuel gas with a high octane number. Using the procedure of U.S. Pat. No. 3,828,736 the fuel gas so formed can be burned in the internal combustion engine with excess air, in which the formation of nitrogen oxides, and the emission of carbon monoxide and other products of an arrested combustion are largely avoided.
A number of catalytically active fillings for the reaction chamber of reformed-gas generators have also been developed which make possible a soot-free reaction of hydrocarbons with air under heavy air deficiency. These fillings usually consist of a ceramic carrier material which contains a particular aluminum oxide. This aluminum oxide is preferably present in thermally unstable catalytically active modifications since the thermally stable .alpha.-Al.sub.2 O.sub.3 only has very little catalytic activity for the partial oxidation. Accordingly, the unstable modification effectively aids the activity of the catalytically active components of the fillings which are usually metal oxides.
It is extremely advantageous to be able to use small amounts of primary air without formation of soot. However, in such situations, known nickel or nickel-containing metal alloys favor the formation of soot. This leads to disturbances in the operation of the combustion device and to contamination of the catalyst which reduces its effectiveness. Also, the catalyst systems described above with ceramic carrier matter cannot suppress soot formation reliably unless the fuel is carefully evaporated before entering the hot reactor. The operation of such known reformed-gas generators requires careful control of the air number since the reaction temperature in the gas generator rises if the amounts of primary air are too large, and the thermally unstable catalysts are damaged. Another disadvantage is that many known catalysts which are used in the prior art processes are sensitive to the use of sulphur-containing fuels. A further disadvantage is that use of the known catalysts required careful control of the process in order to maintain the optimum operating temperature. This is because the known catalysts have relatively low thermal conductivities and, therefore, the danger of uneven temperature distribution and, incomplete conversion in the reaction chamber exists.
It is therefore an object of this invention to provide an improved method for the soot-free conversion of liquid hydrocarbons into a fuel gas which contains carbon-monoxide, hydrogen and gaseous hydrocarbons.
It is another object of this invention to provide an improved method which requires minimum outside control.
It is still another object of this invention to provide an improved method in which sulfur containing hydrocarbons can be used without the possibility of contaminating the environment.
Still other objects and advantages of the present invention will be obvious and apparent to those of skill in the art from the specifications and the appended claims.